Electron discharge tube



March 3, 1936. J. VAN DER MARK ELECTRON DISCHARGE TUBE Original Filed Sept. 24, 1930 INVENTOR- JAN VAN DER MARK BY Q ATTORNEY- Patented Mar. 3, 1936 v ELECTRON DISCHARGE TUBE Jan van der Mark,,Eindhoven, Netherlands, assignor to Radio Corporation of America. a corporation of Delaware Original application September 24, 1930, Serial No. 484,006. Divided and this application November 5, 1932, Serial No. 641,367.

In the Netherlands 0mm 4, 1929 1 Claim. (Cl. 250-415) The present invention is a division of application Serial No. 484,006, filed Sept. 24, 1930, relating to a circuit arrangement for the detection of modulated high frequency oscillations with subsequent amplification for rendering the detected modulation oscillations strongly audible in a loudspeaker. The claim of this application is directed to the tube per se used in such circuits.

The known method of the so-called grid detection has, besides the advantage of a great sensitiveness, the disadvantage of being, with incoming powerful signals, unavoidably attended with anode detection whereby the grid detection is counteracted, and the speech or music is attenuated and distorted. With an increasing high frequency signal the triode, considered as a low frequency amplifier, begins to work on a very unfavorable part of the characteristic curve, which also gives rise to distortion.

The present invention has for its object to provide a circuit arrangement with which the advantage of grid detection remains intact, but with which undesirable anode detection is suppressed while the average potential of the control grid remains constant.

According to the invention, for this purpose, the arrangement is such that detection takes place in a circuit comprising a rectifier and a condenser, the latter being connected on one side to the nonoscillating electrode of the rectifier, and on the other side to the control grid of the amplifier.

According to the invention, use should preferably be made of a thermionic rectifier which has in this case the cathode in. common with the abovementioned, also thermionic, amplifier.

The invention, finally, includes a discharge tube suitable for the realization of the last mentioned circuit arrangement and comprising a cathode which slightly protrudes from the electrode complex (anode and grid or grids) of the amplifier and which is surrounded at this point either entirely or partly by a small auxiliary anode.

The novel features which I believe to be characteristic of my invention are set forth in particuby way of example, some embodiments of the inof a detector amplifier according to the invention.

With the circuit arrangement of Fig. l the received modulated high frequency oscillations are made active, after being amplified, in the tuned anode circuit l of a high frequency valve which is not completely represented. .With this circuit I is inductively coupled a coil 2, one of the ends of which is connected to an auxiliary anode 3 of a thermionic device DA. Its other end is connected to one of the coatings of a grid condenser 4. On the other side, this condenser is connected to the cathode B of the device DA, while across its coatings it has a leakage-resistance 5.

The value of the condenser 4 is so chosen that it offers substantially no resistance to the high frequency carrier oscillations, but opposes an appreciable resistance to low frequency oscillations. The consequence thereof is that the lefthand-coating, the one connected to the coil 2, can oscillate with a low frequency but not with a high frequency whereas the other (right hand) coating of the condenser 4 is connected to earth.

To the said left hand coating of the condenser 4 is connected the control grid 1 of the thermionic device DA. This condenser, consequently, can also oscillate only with low frequency so that within the triode formed by the cathode 6, the control grid 1 and the anode 8, there occurs no detection but only low frequency amplification. The detection, in the form of grid detection, entirely takes place in the circuit 2, 3, 6, 4.

A separating condenser 9, a leakage resistance I0 and a grid biasing battery H are provided in order to be enabled to apply the most favorable bias potential to the control grid 1. Under certain conditions, however, the said three elements may be omitted. The further amplification of the low frequency oscillations is effected in the known manner with the aid of a transformer l2, l3, and of .a final valve A comprising a cathode I6, a grid l4, and an anode ll, whereupon the oscillations are led to a reproducer l8, as phones. 1

larged scale a stem of a detector amplifier valve pinch and is led out of the valve.

The circuit arrangement represented in Fig. 2 only diilfers in that the tunable circuit l is directly located in the detector circuit of the valve DA. In this case it is true that both electrodes of the variable condenser of this circuit oscillate, but the electrode connected to the condenser 4 only oscillates with low frequency, so that there is no risk of hand capacity eilect. Besides, the circuit l is directly coupled with the coil 2 of aerial l9, so that the incoming high frequency oscillations are not previously amplified. This circuit arrangement is particularly suitable for use in the neighborhood of a transmitting. station.

Such is also the case with the'circuit arrangement of Fig. 3 in which thedetector-amplifier DA is at the same time the final valve and supplies a reproducer II. For this purpose, the

valve comprises, in addition to a'control grid 1,.

a screen grid 20 and an auxiliary grid 2| which is connected to the middle 22 of the cathode 6. For the rest the connection is identical to that of the valve DA in Fig. 1.

Finally, Fig. 4 represents to a somewhat enconstructed in accordance with the invention. On the front side the cathode 6, which is supposed to be an equipotential cathode,,-protrudes from the control grid 1 and the anode to such an extent that there is some room for a small auxiliary anode 3 which is spaced closer to its cathode portion than the control grid 1- is spaced from its cathode portion. The leading-in wire for the. auxiliary or rectifier anode 3- simultaneously acts as a support, is sealed intothe The size of the valve consequently remains the same although now it fulfills two quite separate functions, and even is capable of setting up without any distortion considerably higher low frequency voltage variations from modulated high frequency oscillations than could be obtained with the ordinary grid detection and low frequency amplification, consequently with two separated triodes. This is due to the fact that with the circuit-arrangement of thedetector-amplifier according to the inventiomth'e desired linear relation between the amplitudes of the outgoing low frequency and the incoming modulated high frequency oscillations subsists even at high values of the latter amplitudes owing to the fact that there is no v counteracting and finally dominating anode detection.

While I have indicated and described one arrangement forgcarrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means. limited to the particular organizations shown and described, but that many, modifications may be made, without departing from the scope of my invention as set forth in the appended claim.

What 'I claim is: v

, An electron discharge tube comprising an elongated tubular cathode, an amplifier anode surrounding a major portion of said tubular cathode, a control grid spaced from the cathode and interposed between the cathode and the amplifier anode, and a rectifier anode disposed immediately adjacent and surrounding substantially the remaining portion of said cathode for intercepting the electron flow from that portion without the intervention of another electrode,

' said rectifier anode being spaced closer to its cathode portion than the control grid'is spaced from its cathode portion. JAN VAN nan MARK. 

